A cylindrical bucket has 150mL of mud in it. A tennis ball was found in the bucket of the mud. When the tennis ball was removed there was 130mL of mud in the bucket. The mass of the ball is 40g. Find the density of the tennis ball. Please Help ASAP

Amountain climber starts a climb at an elevation of 453 feet above sea level at his first rest stop he has climbed 162 feet and by his second rest stop he has climbed another 207 feet its getting late in the day so the climber starts his way down if the climber desends 285 feet how much does he need to ascend or descend to return to the original starting point